Consider the following ionic compounds: CdCO3, Na2S, PbSO4, (NH4)3PO4, and Hg2Cl2. Which compounds will be soluble when added to water? a. Na2S and (NH4)3PO4
b. Hg2Cl2
c. Hg2Cl2, Na2S, and (NH4)3PO4
d. CdCO3, PbSO4, and Hg2Cl2

a. Na₂S and (NH₄)₃PO₄ .

Explanation:

To know which salts are soluble we need to remember some solubility rules. And apply these as follows:

* All compounds of group 1 (Li⁺, Na⁺, K⁺, etc.) are soluble, Na₂S is soluble.

* All ammonium salts are soluble,

* All Cl⁻, I⁻, Br⁻ are soluble except when are with Ag⁺, Hg₂²⁺, Pb²⁺, Hg₂Cl₂ is insoluble

* Carbonates are insoluble except those with group 1 or ammonium, CdCO₃ is insoluble

* All sulfates are soluble except those with Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, Ag⁺. PbSO₄ is insoluble.

Right solution is:

increased stability in the completion of fluorine's outer shell.